Advances in modeling of lower hybrid current drive
Advances in modeling of lower hybrid current drive
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DOI：
10.1088/0741-3335/58/4/044008
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发表时间：
2016-02
影响因子：
2.2
通讯作者：
Y. Peysson;J. Decker;E. Nilsson;J. Artaud;A. Ekedahl;M. Goniche;J. Hillairet;Bojiang Ding;Miao-Hui Li;P. Bonoli;S. Shiraiwa;M. Madi
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文献类型：
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作者：
Y. Peysson;J. Decker;E. Nilsson;J. Artaud;A. Ekedahl;M. Goniche;J. Hillairet;Bojiang Ding;Miao-Hui Li;P. Bonoli;S. Shiraiwa;M. Madi
托卡马克等离子体中低杂波电流驱动的第一原理模拟是一个长期的活动，由于与实验观测的定量比较，它的精度正在逐渐提高。在这方面，能够同时再现硬X射线(HXR)光子能量范围内的等离子体电流和非热韧致辐射径向分布的能力代表着一项重大成就。尽管受到限制，但光线跟踪计算通常用于描述波的传播与福克-普朗克程序，因为它可以捕捉到托卡马克等离子体环状折射中的LH波动力学的显著特征。这一工具已经在几台机器上得到了验证，当完全吸收LH波需要将一小部分功率从发射功率谱的主瓣转移到具有较高平行折射率的尾部。相反，只有当光谱间隙很大时，基于环形折射的标准建模才会变得更具挑战性，除非其他物理机制可能会主导连接它，如参数不稳定性，就像对喷气左旋光放电所建议的(Cesario等人，2004年物理)。莱特牧师。92 175002)，或发射功率谱或“尾部”LH模型的快速波动，如上文所示(Decker等人，2014Phys.血浆21 092504)。与TORE上述研究相比，启发式“尾部”LH型模型在更宽的等离子体参数范围内的适用性被考察，并且具有不同的LH波特征。根据所使用的不同模型，讨论了模拟和实验之间的差异和一致。发射功率谱中“尾巴”的存在显著改善了EAST和Alcator C-Mod托卡马克中光谱差距较大的等离子体条件下的建模和实验之间的一致性。对于烧结器C-MOD托卡马克，HxR分布随密度的实验演化表明，该模型在线平均密度为n‘e≃1.0x10+20？>；m−3时是有效的，这一结论得到了HxR标度律随密度的模拟的证实。用GENRAY/CQL3D程序模拟的结果表明，HXR辐射随密度的快速下降归因于碰撞阻尼层的寄生吸收，而C3PO/Luke程序提供了另一种解释，该解释是基于左旋波在X点附近传播时的折射增强。文中还讨论了对ITER中氢电流预测的影响。
First principle modeling of the lower hybrid (LH) current drive in tokamak plasmas is a longstanding activity, which is gradually gaining in accuracy thanks to quantitative comparisons with experimental observations. The ability to reproduce simulatenously the plasma current and the non-thermal bremsstrahlung radial profiles in the hard x-ray (HXR) photon energy range represents in this context a significant achievement. Though subject to limitations, ray tracing calculations are commonly used for describing wave propagation in conjunction with Fokker–Planck codes, as it can capture prominent features of the LH wave dynamics in a tokamak plasma-like toroidal refraction. This tool has been validated on several machines when the full absorption of the LH wave requires the transfer of a small fraction of power from the main lobes of the launched power spectrum to a tail at a higher parallel refractive index. Conversely, standard modeling based on toroidal refraction only becomes more challenging when the spectral gap is large, except if other physical mechanisms may dominate to bridge it, like parametric instabilities, as suggested for JET LH discharges (Cesario et al 2004 Phys. Rev. Lett. 92 175002), or fast fluctuations of the launched power spectrum or ‘tail’ LH model, as shown for Tore Supra (Decker et al 2014 Phys. Plasma 21 092504). The applicability of the heuristic ‘tail’ LH model is investigated for a broader range of plasma parameters as compared to the Tore Supra study and with different LH wave characteristics. Discrepancies and agreements between simulations and experiments depending upon the different models used are discussed. The existence of a ‘tail’ in the launched power spectrum significantly improves the agreement between modeling and experiments in plasma conditions for which the spectral gap is large in EAST and Alcator C-Mod tokamaks. For the Alcator C-Mod tokamak, the experimental evolution of the HXR profiles with density suggests that this model is valid up to a line-averaged density of n¯e≃1.0×10+20 ?> m−3, a statement that is confirmed by simulations of the HXR scaling law with density. While simulations with GENRAY/CQL3D codes have ascribed the fast decrease of the HXR emission with density to parasitic absorption in the scrape-off layer by collisional damping, an alternative interpretetation based on an enhanced refraction as the LH wave propagates in the vicinity of the X-point is provided by C3PO/LUKE codes. The consequences for the predictions of LH current in ITER are discussed.